Highly Branched Hydrocarbon Isomerization for an Aromatization Reaction

ABSTRACT

A process for aromatizing hydrocarbons comprises: converting at least a portion of highly branched hydrocarbons in a feed stream into selectively convertible components, and aromatizing the selectively convertible components to produce an aromatization reactor effluent. The aromatization reactor effluent comprises an aromatic product. Converting at least the portion of the highly branched hydrocarbons into the selectively convertible components may include contacting the feed stream with an isomerization catalyst in an isomerization reaction system under isomerization reaction conditions; and isomerizing the portion of the highly branched hydrocarbons in the feed stream into the selectively convertible components.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 15/188,567 filed Jun. 21, 2016, and entitled“Highly Branched Hydrocarbon Isomerization for an AromatizationReaction,” which is incorporated by reference herein in its entirety.

FIELD

This disclosure relates generally to a system and method for continuallyoperating an aromatization process. More particularly, the disclosurerelates to continually operating an aromatization process whileconverting highly branched hydrocarbons within the system to convertiblecomponents.

BACKGROUND

Typical aromatization processes may be carried out using a variety ofreactors containing dehydrocyclization catalysts. The aromatizationprocess encompasses a number of reactions, which are typically carriedout in the presence of a catalyst, such as dehydrocyclization,hydrodecyclization, isomerization, hydrogenation, dehydrogenation,hydrocracking, cracking, or combinations thereof. Aromatizationreactions are intended to convert paraffins, naphthenes, and olefins toaromatics and hydrogen.

The feed stream may comprise components that may be difficult to convertin the aromatization process. These components may build up in recycleloops and are typically removed through separation within the system.Alternatively, an upstream process may be used to reduce the amount ofnon-convertible components in the feed stream.

SUMMARY

An aspect of the disclosure includes a process for aromatizinghydrocarbons that comprises converting at least a portion of highlybranched hydrocarbons in a feed stream into selectively convertiblecomponents, and aromatizing the selectively convertible components in anaromatization reaction zone to produce an aromatization reactoreffluent. The aromatization reactor effluent comprises an aromaticproduct. Converting at least the portion of the highly branchedhydrocarbons into the selectively convertible components may includecontacting the feed stream with an isomerization catalyst containedwithin an isomerization reactor in an isomerization reactor system underisomerization reaction conditions; and isomerizing the portion of thehighly branched hydrocarbons in the feed stream into the selectivelyconvertible components. The isomerization catalyst may comprise a βzeolite. The isomerization catalyst may comprise a Group 10 metal,and/or the isomerization catalyst may comprise between about 0.1 wt. %and about 1 wt. % platinum on the β zeolite. A silicon to aluminum molarratio of the β zeolite may be between about 20 to about 60.

The highly branched hydrocarbons may comprise hydrocarbons having six orseven carbon atoms with an internal quaternary carbon or hydrocarbonshaving six carbons atoms and two adjacent internal tertiary carbons ormixtures thereof. The highly branched hydrocarbons may comprisedimethylbutanes, trimethylbutanes, dimethylpentanes, or mixturesthereof. The highly branched hydrocarbons with six or seven carbon atomswith an internal quaternary carbon may comprise, for example,2,2-dimethylbutane, 2,2-dimethylpentane, 3,3-dimethylpentane,2,2,3-trimethylbutane, or mixtures thereof. The highly branchedhydrocarbons with six carbon atoms and an adjacent internal tertiarycarbons may comprise 2,3-dimethylbutane. The highly branchedhydrocarbons do not easily convert to aromatic products and instead tendto convert to light hydrocarbons.

The selectively convertible components may comprise hydrocarbons havingsix or seven carbon atoms without an internal quaternary carbon orhydrocarbons having six carbon atoms without two adjacent internaltertiary carbons, or mixtures thereof. The selectively convertiblecomponents may comprise methylpentanes, methylhexanes, dimethylpentanesor mixtures thereof, and/or the selectively convertible components maycomprise at least one of 2-methylpentane, 3-methylpentane,2,4-dimethylpentane, 2,3-dimethylpentane, n-hexane, 2-methylhexane,3-methylhexane, n-heptane, or mixtures thereof. The feed stream maycomprise between about 0.1 wt. % and about 100 wt. % highly branchedhydrocarbons. The selectively convertible components readily convert toaromatic products without production of light hydrocarbons.

Aromatizing the selectively convertible components may comprisecontacting the selectively convertible components with adehydrocyclization catalyst in an aromatization reaction zone underaromatization reaction conditions, and converting the selectivelyconvertible components into one or more aromatics in the aromaticproduct. The dehydrocyclization catalyst may comprise at least one GroupVIII metal and zeolitic support. The least one Group VIII metal maycomprise platinum and the zeolitic support comprises silica boundL-zeolite. The dehydrocyclization catalyst may comprise one or morehalogens. The aromatization reactor effluent may comprise the highlybranched hydrocarbons, and the process may also include: separating atleast a portion of the aromatic product from the aromatization reactoreffluent to obtain a raffinate stream, where the raffinate stream has anincreased highly branched hydrocarbon concentration compared to thearomatization reactor effluent; and providing the raffinate stream tothe isomerization reactor system as the feed stream. The aromatizationreactor effluent may comprise the highly branched hydrocarbons, and theprocess may also include: separating at least a portion of the aromaticproduct from the aromatization reactor effluent to obtain a raffinatestream, where the raffinate stream has an increased highly branchedhydrocarbon concentration compared to the aromatization reactoreffluent; and separating the highly branched hydrocarbons from theraffinate stream to obtain the feed stream to the isomerization reactorsystem, where the feed stream has an increased highly branchedhydrocarbon concentration compared to the lean raffinate stream. Thearomatization reactor effluent may comprise the highly branchedhydrocarbons, and the process may also include: separating at least aportion of the highly branched hydrocarbons from the aromatizationreactor effluent to obtain a highly branched hydrocarbon stream, wherethe highly branched hydrocarbon stream has an increased highly branchedhydrocarbon concentration compared to the aromatization reactoreffluent; and providing the highly branched hydrocarbon stream to theisomerization reactor system as the feed stream.

In further aspects of the disclosure is a process for aromatizinghydrocarbons comprises recovering highly branched hydrocarbons in anaromatization reactor effluent produced in an aromatization reactionzone; converting at least a portion of the highly branched hydrocarbonsinto selectively convertible components; and aromatizing the selectivelyconvertible components to produce an aromatic product. The process mayalso include feeding the selectively convertible components to an inletof an aromatization reactor system, where the aromatization reactorsystem produces the aromatization reactor effluent wherein thearomatization reactor system comprises at least one aromatizationreactor and at least one furnaces located upstream of each reactor toheat the streams prior to entering an aromatization reactor in thearomatization reactor system. Converting at least the portion of thehighly branched hydrocarbons may comprise contacting the highly branchedhydrocarbons with an isomerization catalyst in at least oneisomerization reactor within an isomerization reactor system, andisomerizing at least the portion of the highly branched hydrocarbonsinto the selectively convertible components. The isomerization catalystmay comprise a β zeolite and a Group 10 metal. The selectivelyconvertible components may comprise at least one of 2-methylpentane,3-methylpentane, 2,4-dimethylpentane, 2,3-dimethylpentane, n-hexane,2-methylhexane, 3-methylhexane, n-heptane, or mixtures thereof.

In some aspects, a process for aromatizing hydrocarbons comprises:concentrating highly branched hydrocarbons in a hydrocarbon stream toyield a highly branched hydrocarbon rich stream, converting at least aportion of the highly branched hydrocarbons in the highly branchedhydrocarbon rich stream into selectively convertible components, andaromatizing the selectively convertible components in an aromatizationreactor system to produce an aromatization reactor effluent comprisingan aromatic product. Concentrating the highly branched hydrocarbons maycomprise separating aromatics from the hydrocarbon stream to yield thehighly branched hydrocarbons rich stream. Concentrating the highlybranched hydrocarbons may also comprise separating at least a portion ofthe highly branched hydrocarbons from the hydrocarbon stream to yieldthe highly branched hydrocarbons rich stream. The hydrocarbon stream maybe an aromatization reactor effluent. Converting at least the portion ofthe highly branched hydrocarbons into selectively convertible componentsmay comprise contacting the highly branched hydrocarbons with anisomerization catalyst, and isomerizing at least the portion of thehighly branched hydrocarbons into the selectively convertiblecomponents. The isomerization catalyst may comprise a β zeolite andplatinum.

In various aspects, an aromatization reactor system comprises at leastone aromatization reactor comprising a dehydrocyclization catalyst, afeed inlet, and an aromatization reactor effluent outlet; a separator influid communication with the aromatization reactor effluent outlet, andan isomerization reactor system comprising an isomerization catalystcontained within at least one isomerization reactor. The separator isconfigured to separate at least a portion of an aromatization reactoreffluent stream comprising an aromatic product and highly branchedhydrocarbons into an aromatic product stream enriched in aromatics and ahighly branched hydrocarbon stream enriched in the highly branchedhydrocarbons. The separator is also configured to pass the highlybranched hydrocarbon stream out of a highly branched hydrocarbon streamoutlet, and the isomerization reactor system is in fluid communicationwith the highly branched hydrocarbon stream outlet to receive the highlybranched hydrocarbon stream. The isomerization reactor system isconfigured to isomerize at least a portion of the highly branchedhydrocarbons in the highly branched hydrocarbon stream into selectivelyconvertible components, and an outlet of the isomerization reactorsystem is in fluid communication with the feed inlet of thearomatization reactor system to pass at least a portion of theselectively convertible components from the isomerization reactor systemto the aromatization reaction zone. The isomerization catalyst maycomprise a β zeolite, and a silicon to aluminum molar ratio of the βzeolite may be between about 20 to about 60. The isomerization catalystmay comprise a Group 10 metal. The isomerization catalyst may comprisebetween about 0.1 wt. % and about 1 wt. % platinum on the β zeolite. Thedehydrocyclization catalyst may comprise at least one Group VIII metaland zeolitic support. The least one Group VIII metal may compriseplatinum and the zeolitic support comprises silica bound L-zeolite,and/or the dehydrocyclization catalyst comprises one or more halogens.

These and other features will be more clearly understood from thefollowing detailed description taken in conjunction with theaccompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic flow diagram of some aspects of an aromatizationprocess of the disclosure.

FIG. 2 is another schematic flow diagram of various aspects of anaromatization process of the disclosure.

FIG. 3 is a graphical representation of the results of an isomerizationusing some aspects of a catalyst as described herein.

FIG. 4 is another graphical representation of the results of anisomerization using some aspects of a catalyst as described herein.

FIG. 5 is still another graphical representation of the results of anisomerization using some aspects of a catalyst as described herein.

FIG. 6 is yet another graphical representation of the results of anisomerization using some aspects of a catalyst as described herein.

FIG. 7 is another graphical representation of the results of anisomerization using some aspects of a catalyst as described herein.

FIG. 8 is still another graphical representation of the results of anisomerization using some aspects of a catalyst as described herein.

DETAILED DESCRIPTION

As is generally understood, an aromatization “reaction”, typically takesplace within an aromatization “reactor.” The reactor(s) employed in thisprocesses described herein may be any conventional type of reactor thatmaintains a catalyst within the reactor and may accommodate a continuousflow of hydrocarbon. The aromatization reactor systems described hereinmay comprise a fixed catalyst bed system, a moving catalyst bed system,a fluidized catalyst bed system, or combinations thereof. Suitablereactors may include, but are not limited to, fixed bed reactorsincluding radial flow reactors, bubble bed reactors, or ebullient bedreactors. The flow of the feed stream may be upward, downward, orradially through the reactor. In various aspects, the aromatizationreactor system described herein may be operated as a series of adiabaticreactors or an isothermal reactor system. As used herein, a “hydrocarbonstream” comprises hydrocarbons, though components other than moleculescomprising hydrogen and carbon may be present in the stream (forexample, hydrogen gas). In some aspects, a “hydrocarbon” may compriseindividual molecules that comprise one or more atoms other than hydrogenand carbon (for example, nitrogen, oxygen, or mixtures thereof.).

Disclosed herein is a system and process for converting a hydrocarbonfeed stream comprising branched components into an aromatic product. Thefeed stream may comprise various components that are difficult toconvert to aromatic products. For example, dimethylbutanes (DMBs) may bedifficult to convert to an aromatic product due to the high degree ofbranching. These highly branched compounds may generally build up inrecycle loops if they are present so that these components must beseparated and removed from the system. While some highly branchedcompounds are difficult to convert to aromatic products, the isomers ofthe branched compounds may be more easily converted. For example, theisomers of dimethylbutanes including 2-methyl pentane, 3-methyl pentane,and n-hexane are all capable of being converted in an aromatizationprocess to aromatic products.

As disclosed herein, an isomerization process may be incorporated intothe aromatization process. In this process, the highly branchedhydrocarbons may be concentrated and passed to an isomerization reactorsystem. By operating at the appropriate conditions, the highly branchedhydrocarbons may be isomerized into selectively convertible components.These selectively convertible components may then be passed to thearomatization process to convert the selectively convertible componentsinto aromatic products.

An aromatization system 100 is shown in FIG. 1. At the inlet of theprocess, a fresh hydrocarbon stream comprising unreacted hydrocarbons isfed through line 102, which may be combined with one or more recyclestreams in line 120 and one or more isomerized streams in line 126before passing to the aromatization reactor system 106. Various feedstreams may be suitable for use with aromatization processes, and thefeed stream may comprise components that may be converted in thearomatization process and components that may not be readily convertedto aromatic products. As used herein, the term “selectively convertiblecomponents” refers to hydrocarbon components that may be converted toaromatic products such as aromatic hydrocarbons within the aromatizationreactor system 106. The selectively convertible components may notcomprise an internal quaternary carbon, or hydrocarbons having sixcarbon atoms and two adjacent internal tertiary carbon atoms, ormixtures thereof.

The selectively convertible components may generally comprisenon-aromatic hydrocarbons. The selectively convertible components in thefeed stream to the aromatization system 100 comprising an aromatizationreactor system 106 may comprise a mixture of hydrocarbons comprising C₆to C₇ hydrocarbons containing up to about 10 wt % and alternatively upto about 15 wt % of C₅ and lighter hydrocarbons (C₅ ⁻) and containing upto about 25 wt % of C₈ and heavier hydrocarbons (C₈ ⁺). For example, thefeed stream may include naphtha boiling range hydrocarbons comprising amajority of C₆-C₇ paraffins. In some aspects, the feed stream preferablyis C₆ or higher non-aromatic organic compounds. Non-limiting examples ofpreferred C₆-C₇ paraffinic feed stream components include n-hexane, orn-heptane. The selectively convertible components may also comprisebranched hydrocarbons including, but not limited to, methylpentanes (forexample, 2-methylpentane, 3-methylpentane), methylhexanes (for example,2-methylhexane, 3-methylhexane), and mixtures thereof.

Examples of suitable feed streams include straight-run naphthas frompetroleum refining or fractions thereof that have been hydrotreated toremove sulfur and other catalyst poisons. Also suitable are syntheticnaphthas or naphtha fractions derived from other sources such as coal,natural gas, or from processes such as Fischer-Tropsch processes, fluidcatalytic crackers, and hydrocrackers. In various aspects, the naphthafeed stream may be derived directly from crude petroleum bydistillation, or may be indirectly derived from a petroleum feed streamby separation of a naphtha boiling range stream from the effluent fromhydrocracking, coking or catalytic cracking.

The feed stream may also comprise various highly branched hydrocarbonsthat may not be converted in the aromatization reactor system 106. Thesehydrocarbons may have boiling points close to the selectivelyconvertible components in the feed stream and be present in the feedstream as a result of upstream processing. For example, dimethylbutanesboil near n-hexane, and also near methylpentanes, both of which may beused as feed streams for the aromatization reactor system 106. In someaspects, the feed stream comprises a highly branched hydrocarbon that isnot readily converted to an aromatic compound in the aromatizationreactor system 106. As used herein a “highly branched hydrocarbons”refer to hydrocarbons having six or seven carbon atoms with at least oneinternal quaternary carbon, or hydrocarbons having six carbon atoms andat least two adjacent internal tertiary carbon atoms, or mixturesthereof regardless of total molecular weight or carbon atom content. Thehighly branched hydrocarbons may include, but are not limited to,dimethylbutanes (for example, 2,2-dimethylbutane, 2,3-dimethylbutane),dimethylpentanes (for example, 2,2-dimethylpentane,3,3-dimethylpentane), trimethylbutanes (for example,2,2,3-trimethylbutane) and mixtures thereof.

The amount of highly branched hydrocarbons in the fresh hydrocarbonstream 102 to the aromatization system 100 may vary based on the sourceof the feed stream. In some aspects, the net unreacted hydrocarbon inthe feed stream to the process may contain from about 0.1 wt. % to about20 wt. %, from about 0.3 wt. % to about 18 wt. %, or from about 0.5 wt.% to about 15 wt. % highly branched hydrocarbons, based on weight of thenet or unreacted hydrocarbon in the feed stream to the process. The term“unreacted hydrocarbon” is used herein refers to the net hydrocarbon inthe feed stream to the process which has not been passed through thearomatization reactor system 106. While described as having an upperlimit, the composition of the feed stream, including the unreactedhydrocarbon, may have higher amounts of highly branched hydrocarbons,where the isomerization reactor system may convert the highly branchedhydrocarbons into selectively convertible components. As a result, thefeed stream, which may include the unreacted hydrocarbon, may comprisebetween about 0.1 wt. % and about 100 wt. % of the highly branchedhydrocarbons, where the highly branched hydrocarbons may be convertedinto selectively convertible components within the aromatization system100.

While not shown in FIG. 1, various upstream hydrocarbon pretreatmentsteps may be used to prepare the hydrocarbon for the aromatizationprocess. For example, hydrotreating may be used to remove catalystpoisons such as sulfur. Contacting the hydrocarbon with a nickelcatalyst, for example, prior to the aromatization reaction may alsoprotect against failure of the hydrotreating system. In various aspects,the hydrocarbon stream may have a sulfur content ranging from less than200 ppbw, alternatively less than 100 ppbw, alternatively from about 10parts per billion by weight (ppbw) to about 100 ppbw.

The fresh hydrocarbon stream passing through line 102 may be combinedwith one or more recycle streams in line 120 and one or more isomerizedstreams in line 126. These streams (120, 126 or both) may containhydrogen, unreacted selectively convertible components, and/or highlybranched hydrocarbons that have been isomerized into selectivelyconvertible components. The combined feed stream passing through line104 may then pass to the aromatization reactor system 106. Variousequipment may be used to modify or adjust the conditions of the streamsprior to entering the aromatization reactor system 106 such as heatexchangers, pumps, treating units (for example, sulfur removal systems),and the like.

The aromatization reactor system 106 may comprise one or more reactorsto contact the selectively convertible components in the feed streamwith a dehydrocyclization catalyst under aromatization reactionconditions to form aromatic components. As the aromatization reaction isgenerally endothermic, the combined feed stream in line 104 may beheated in one or more furnaces prior to introduction to each of the oneor more aromatization reactors. The one or more furnaces and one or morearomatization reactors are not shown as separate features of thearomatization reactor system 106.

In some aspects, the aromatization reactor system 106 may comprise aplurality of reactors arranged in series. Heaters such as furnaces maybe located upstream of each reactor to heat the streams prior toentering an aromatization reactor in the aromatization reactor system.The furnaces may comprise any type of furnace capable of raising thetemperature of the reactant stream to achieve the desired inlettemperature to the subsequent reactor. The temperature may be raised sothat the aromatization reactions proceed in the subsequent reactors,which is generally needed due to the endothermic nature of thearomatization process. The aromatization reactor system 106 maycomprises three or more serially connected reactors, and all of thereactors may be the same or different in size or configuration. Invarious aspects, all of the reactors may be radial flow reactors withthe hydrocarbon stream passing through the reactors in inward or outwardflow. In some aspects, the reactors may be sized according to knowntechniques, and all of the reactors may be the same size. Alternatively,one or more reactors may be different sizes.

In general, the aromatization reactions occur under process conditionsthat thermodynamically favor the aromatization reactions and limitundesirable hydrocracking reactions. The aromatization reaction may becarried out using any conventional aromatization conditions, and may becarried out at reactor inlet temperatures ranging from about 600° F. toabout 1100° F., alternatively from about 650° F. to about 1100° F.,alternatively from about 700° F. to about 1100° F., alternatively fromabout 800° F. to about 1050° F., alternatively from about 850° F. toabout 1050° F. Reaction pressures may range from about atmosphericpressure to about 500 psig, alternatively from about 25 psig to about300 psig, and alternatively from about 30 psig to about 100 psig. Themolar ratio of hydrogen to hydrocarbon in the combined feed stream 104is normally between about 0.1 and about 10, alternatively from about 0.5to about 5.0, and alternatively from about 1:1 to about 3:1. The liquidhourly space velocity (LHSV) for the feed stream over thedehydrocyclization catalyst is from about 0.5 hr⁻¹ to about 20 hr⁻¹, andalternatively from about 0.50 hr⁻¹ to about 5.0 hr⁻¹ based on thecatalyst in the aromatization reactor system 106.

In various aspects, the aromatization reactors in the aromatizationreactor system 106 may each contain a dehydrocyclization catalyst forcarrying out an aromatization process. As is known to those of ordinaryskill in the art, a suitable dehydrocyclization catalyst is capable ofconverting at least a portion of aliphatic and/or naphthenichydrocarbons (for example, non-aromatic hydrocarbons) in a hydrocarbonstream to aromatic hydrocarbons. Any catalyst capable of carrying out anaromatization reaction may be used alone or in combination withadditional catalytic materials in the reactors. Suitable catalysts mayinclude acidic or non-acidic catalysts. In some aspects, the catalyst isa non-acidic catalyst. A suitable non-acidic catalyst may comprise anon-acidic zeolite support, at least one group VIII metal, and one ormore halides. Suitable halides include chloride, fluoride, bromide,iodide, or combinations thereof. Suitable Group VIII metals includeiron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium,platinum, or combinations thereof. Examples of catalysts suitable foruse with the aromatization reactor system described herein are AROMAX®catalysts available from the Chevron Phillips Chemical Company LP of TheWoodlands, Tex., and those discussed in U.S. Pat. No. 6,812,180 toFukunaga entitled “Method for Preparing Catalyst” and U.S. Pat. No.7,153,801 to Wu entitled “Aromatization Catalyst and Methods of Makingand Using Same,” each of which is incorporated herein by reference as ifreproduced in their entirety.

The supports for catalysts may generally include any inorganic oxide.These inorganic oxides may include bound large pore aluminosilicates(zeolites), amorphous inorganic oxides and mixtures thereof. Large porealuminosilicates may include, but are not limited to, L-zeolite,Y-zeolite, mordenite, omega zeolite, beta zeolite, and the like.Amorphous inorganic oxides may include, but are not limited to, aluminumoxide, silicon oxide, and titania. Suitable bonding agents for theinorganic oxides may include, but are not limited to, silica, alumina,clays, titania, and magnesium oxide.

Zeolite materials, both natural and synthetic, are known to havecatalytic properties for many hydrocarbon processes. Zeolites typicallyare ordered porous crystalline aluminosilicates having structure withcavities and channels interconnected by channels. The cavities andchannels throughout the crystalline material generally may be of a sizeto allow selective separation of hydrocarbons.

The term “zeolite” generally refers to a particular group of hydrated,crystalline metal aluminosilicates. These zeolites exhibit a network ofSiO₄ and AlO₄ tetrahedra in which aluminum and silicon atoms arecrosslinked in a three-dimensional framework by sharing oxygen atoms. Inthe framework, the ratio of oxygen atoms to the total of aluminum andsilicon atoms may be equal to about 2. The framework exhibits a negativeelectrovalence that typically is balanced by the inclusion of cationswithin the crystal such as metals, alkali metals, alkaline earth metals,or hydrogen.

L-type zeolite catalysts are a sub-group of zeolitic catalysts. TypicalL-type zeolites contain mole ratios of oxides in accordance with thefollowing formula:

M2/nOAl₂O₃xSiO₂yH₂O

wherein “M” designates at least one exchangeable cation such as barium,calcium, cerium, lithium, magnesium, potassium, sodium, strontium, andzinc as well as non-metallic cations like hydronium and ammonium ionswhich may be replaced by other exchangeable cations without causing asubstantial alteration of the basic crystal structure of the L-typezeolite. The “n” in the formula represents the valence of “M”, “x” is 2or greater; and “y” is the number of water molecules contained in thechannels or interconnected voids with the zeolite. Bound potassiumL-type zeolites, or KL zeolites, have been found to be particularlydesirable. The term “KL zeolite” as used herein refers to L-typezeolites in which the principal cation M incorporated in the zeolite ispotassium. A KL zeolite may be cation-exchanged or impregnated withanother metal and one or more halides to produce a platinum-impregnated,halided zeolite or a KL supported Pt-halide zeolite catalyst.

In various aspects, the at least one Group VIII metal is platinum. Inother aspects, the at least one Group VIII metal is platinum and gold.In still further aspects, the at least one Group VIII metal is platinumand rhenium. The platinum and optionally one or more halides may beadded to the zeolite support by any suitable method, for example viaimpregnation with a solution of a platinum-containing compound and oneor more halide-containing compounds. For example, theplatinum-containing compound may be any decomposable platinum-containingcompound. Examples of such compounds include, but are not limited to,ammonium tetrachloroplatinate, chloroplatinic acid, diammineplatinum(II) nitrite, bis-(ethylenediamine)platinum (II) chloride, platinum (II)acetylacetonate, dichlorodiammine platinum, platinum (II) chloride,tetraammineplatinum (II) hydroxide, tetraammineplatinum chloride, andtetraammineplatinum (II) nitrate.

In some aspects, the catalyst is a zeolitic support with aplatinum-containing compound and at least one ammonium halide compound.The ammonium halide compound may comprise one or more compoundsrepresented by the formula N(R)₄X, where X is a halide and where Rrepresents a hydrogen or a substituted or unsubstituted carbon chainmolecule having 1-20 carbons wherein each R may be the same ordifferent. In various aspects, R is selected from the group consistingof methyl, ethyl, propyl, butyl, and combinations thereof, morespecifically methyl. Examples of suitable ammonium compounds arerepresented by the formula N(R)₄X include ammonium chloride, ammoniumfluoride, and tetraalkylammonium halides such as tetramethylammoniumchloride, tetramethylammonium fluoride, tetraethylammonium chloride,tetraethylammonium fluoride, tetrapropylammonium chloride,tetrapropylammonium fluoride, tetrabutylammonium chloride,tetrabutylammonium fluoride, methyltriethylammonium chloride,methyltriethylammonium fluoride, and combinations thereof.

The catalyst may be employed in any of the conventional types orstructures known to the art. It may be employed in the form ofextrudates, pills, pellets, granules, broken fragments, or variousspecial shapes, disposed within the aromatization reactor system 106(for example, in a fixed bed), and the charging stock may be passedtherethrough in the liquid, vapor, or mixed phase, and in either upwardor downward, or inward or outward flow.

The selectivity for converting the selectively convertible components toaromatics is a measure of the effectiveness of the aromatizationreaction in converting selectively convertible components to the desiredand valuable products: aromatics and hydrogen, as opposed to the lessdesirable by-products, such as products from hydrocracking in thearomatization reactor system 106. The dehydrocyclization catalyst isused under reaction conditions effective to achieve per pass conversionof selectively convertible components to aromatics and otherhydrocarbons of at least 50 wt. %, more preferably at least 60 wt. %,and most preferably at least 70 wt. %. The yield of desired aromaticsproduct, on a per pass basis, is the per pass conversion times theselectivity. The term “selectivity” as used herein is defined as apercentage of moles of selectively convertible components converted toaromatics compared to moles converted to aromatics and other products(for example, cracked products). Thus, percent selectivity forselectively convertible components may be defined by the followingformula: Selectivity=(100×moles of selectively convertible componentsconverted to aromatics)/(moles of selectively convertible componentsconverted to aromatics and other products). Isomerization of paraffinsand interconversion paraffins and alkylcyclopentanes having the samenumber of carbon atoms per molecule are not considered in determiningselectivity.

The aromatization product stream from the aromatization reactor system106 may pass to a gas separation zone 107 through line 105, where gassuch as hydrogen present in the aromatization product stream can beseparated into one or more gaseous streams. The hydrogen separated inthe gas separation zone 107 may be recycled to the aromatizationreaction system 106 through line 130, which may be combined with anotherrecycle line such as recycle line 120 and combined with the freshhydrocarbon stream 102 upstream of the aromatization reactor system 106.A hydrogen product stream, line 109, can also be produced in the gasseparation zone 107. The hydrogen product stream can pass out of thesystem 100, or be used for any other purposes within the system 100.

The remaining components from aromatization reaction zone 106, havingpassed through the gas separation zone 107, passes through line 108 toan aromatic separation zone 110, where the aromatic separation zone 110may comprise a series of separation steps. Within the aromaticseparation zone 110, a separation step may be carried out on thearomatic product to separate the aromatic hydrocarbons from thenon-aromatic hydrocarbons. A product stream rich in aromatic materialmay be withdrawn through line 112 from the aromatic separation zone 110.The product stream rich in the aromatic material may leave the systemand/or pass through one or more downstream treatment steps for furtherprocessing. In various aspects, the product stream rich in the aromaticmaterial may comprise more than 80 wt. %, more than 90 wt. %, or morethan 95 wt. % by weight aromatic components. The separated non-aromaticcomponents may be withdrawn as a raffinate stream through line 114. Theseparation of the aromatics from the non-aromatics in the aromaticsseparation zone 110 may be done by any suitable separation processincluding, but not limited to, extraction using a solvent, distillation,and/or by the use of molecular sieves. In any of these separationprocesses, the term “raffinate” is used to refer to the paraffins richstream separated from the aromatics product. In some aspects, the term“rich in paraffins” is used to mean more than 50 wt. % by weightparaffins, or alternatively, more than 80 wt. % paraffins.

The separation in the aromatics separation zone 110 may be carried outby extractive distillation to separate the “raffinate” stream, which isrich in non-aromatics, from the aromatization product stream in line108.

In some aspects, the raffinate stream may be separated from thearomatics in the aromatics separation zone 110 with the aid of asolvent. In these aspects, the aromatics may be absorbed into a solventand thereby extracted from the aromatic product stream as an aromaticsrich stream. In other aspects, the aromatics are combined with a solventand the aromatic-solvent azeotrope is separated by distillation as anaromatics rich stream. The extracted aromatics in the aromatics richstream may be separated from the solvent through a distillation processand the solvent may be recycled. Suitable solvents that may be used insuch a solvent extraction method may include phenol, sulfolane, andN-formyl morpholine. An example of an extractive distillation process isdescribed in U.S. Pat. No. 5,401,365, the disclosure of which isincorporated herein by reference in its entirety.

The raffinate stream in line 114 may comprise the unreacted selectivelyconvertible components and the highly branched hydrocarbons fed to thearomatization reactor system 106, as well as minor amounts of reactionproducts from the aromatization reactor system 106. In various aspects,the raffinate stream may comprise between about at least about 5 wt. %,10 wt. %, 20 wt. %, 30 wt. %, 40 wt. %, or 50 wt. % of the highlybranched hydrocarbons. The raffinate stream in line 114 may then pass toa highly branched hydrocarbon (“HBH”) separation zone 116 that isconfigured to further separate the highly branched hydrocarbons from theselectively convertible components in the raffinate stream.

Alternatively, molecular sieves may be used to separate productaromatics from the paraffins rich raffinate stream by passing theproduct stream comprising aromatics and paraffins through a bed ofmolecular sieves. The molecular sieves tend to adsorb the paraffins, butnot the aromatic components.

In order to convert at least a portion of the highly branchedhydrocarbons to selectively convertible components in an isomerizationreactor system 122, the raffinate stream may be further separated into astream rich in highly branched hydrocarbons and another streamcomprising the selectively convertible components, which may be recycledto the inlet of the aromatization reactor system 106 through recyclestream in line 120 without passing through the isomerization reactorsystem 122. The raffinate stream may be separated using any suitableseparation processes on one or more separation sections within the HBHseparation zone 116. In several aspects, a stream rich in highlybranched hydrocarbons may be separated from the raffinate stream bydistillation in the HBH separation zone 116. The distillation step maybe carried out in one or more distillation columns, using conventionaldistillation techniques conducted in accordance with the removalrequirements for the highly branched hydrocarbons present in theraffinate stream. Other suitable separation processes may also be usedsuch as adsorption, membrane separation, or other separationtechnologies. When the HBH separation zone 116 comprises multipleseparation sections, the different separation sections may use the sameor different separation processes.

The separation within the HBH separation zone 116 may separate at leastabout 60 wt. %, at least about 70 wt. %, at least about 80 wt. %, atleast about 90 wt. % or at least about 95 wt. % of the highly branchedhydrocarbons in the raffinate stream in line 114 into a stream rich inthe highly branched hydrocarbons (“HBH Rich Stream”) in line 118 passingout of the HBH separation zone 116. In various aspects, the separationwithin the HBH separation zone 116 may separate at least about 60 wt. %,at least about 70 wt. %, at least about 80 wt. %, at least about 90 wt.% or at least about 95 wt. % of the dimethylbutanes in the raffinatestream in line 114.

The HBH separation zone 116 may result in a recycle stream in line 120comprising a majority of selectively convertible components with a minoramount of highly branched hydrocarbons and aromatics. In some aspects,the recycle stream in line 120 may comprise less than about 15 wt. %,less than about 10 wt. %, or less than about 8 wt. % highly branchedhydrocarbons, based on the total weight of the recycle stream in line120. The recycle stream may pass back to the inlet of the aromatizationreactor system 106. The recycle stream may be combined with the freshhydrocarbon stream 102 prior to entering the aromatization reactorsystem 106, and/or pass directly to one or more reactors within thearomatization reaction system 106.

A stream rich in highly branched hydrocarbons may also be produced inthe HBH separation zone 116 and pass through line 118 to anisomerization reactor system 122. The concentration of the highlybranched hydrocarbons in the stream in line 118 may be greater thanabout 50 wt. %, greater than about 60 wt. %, greater than about 70 wt.%, or greater than about 80 wt. %, based on the weight of all componentsin the stream in line 118.

The stream rich in the highly branched hydrocarbons may pass to theisomerization reactor system 122. Additional streams that may comprisehighly branched hydrocarbons may also be fed to the isomerizationreactor system 122 through one or more lines such as optional line 124.Various processing streams may be used with the present system 100, andstreams rich in highly branched hydrocarbons may be fed to theisomerization reactor system 122 as an entry point into thearomatization system 100. This may allow the highly branchedhydrocarbons to be isomerized into selectively convertible componentsprior to entering the aromatization reactor system 106. In some aspects,a feed stream comprising highly branched hydrocarbons may be initiallyfed to the aromatization system 100 through line 124 in addition to orin place of the fresh hydrocarbon stream 102 to allow the highlybranched hydrocarbons to be isomerized prior to passing to thearomatization reactor system 106.

The stream rich in the highly branched hydrocarbons in line 118 and anyoptional inlet streams in line 124 may pass to the isomerization reactorsystem 122. The isomerization reactor system 122 may comprise one ormore reactors to contact the highly branched hydrocarbons in the streamrich in the highly branched hydrocarbons with an isomerization catalystunder isomerization reaction conditions to form selectively convertiblecomponents. While not shown in isomerization reactor system 122,hydrogen may optionally be introduced during the isomerization process.The isomerization reaction may be carried out in one or more reactorvessels within the isomerization reactor system 122 shown in FIG. 1.

In various aspects, the reactor(s) in the isomerization reactor system122 may contain a catalyst for carrying out an isomerization process. Asuitable isomerization catalyst is capable of converting at least aportion of the highly branched hydrocarbons into selectively convertiblecomponents. For example, a highly branched hydrocarbon comprising aquaternary carbon atom may be isomerized to a selectively convertiblecomponent comprising two tertiary carbon atoms, where the two tertiarycarbon atoms are not adjacent to each other. Similarly, a highlybranched hydrocarbon comprising two tertiary carbon atoms that areadjacent may be isomerized to a selectively convertible component havingtwo tertiary carbon atoms that are not adjacent, a selectivelyconvertible component having only one tertiary carbon atom (without anyquaternary carbon atoms), or a selectively convertible component thatdoes not have any quaternary or tertiary carbon atoms (for example, anormal paraffin). It should be noted that the isomerization of a highlybranched hydrocarbon may proceed through another highly branchedhydrocarbon before isomerization to a selectively convertible component.

Any catalyst capable of carrying out an isomerization reaction may beused alone or in combination with additional catalytic materials in thereactors. In some aspects, the isomerization catalyst may comprise aplatinum alumina catalyst with or without a Friedel-Crafts halide,platinum molecular sieve catalyst, or platinum sulfate metal oxidecatalyst. In some aspects, the isomerization catalyst may comprise achlorided platinum alumina catalyst. The alumina may include ananhydrous gamma-alumina. The catalyst may also contain other platinumgroup metals. The term platinum group metals refer to noble metalsexcluding silver and gold selected from the group consisting ofplatinum, palladium, ruthenium, rhodium, osmium, and iridium. Thecatalyst may contain from about 0.01 wt. % to about 5 wt. % of theplatinum. Other platinum group metals may be present in a concentrationof from 0.01 wt. % to about 5 wt. %. The platinum component may existwithin the final catalytic composite as an oxide, a halide, or as anelemental metal. The presence of the platinum component in its reducedstate has been found most suitable for this process. The chloridecomponent may be present in an amount from about 2 wt. % to about 10 wt.% based upon the dry support material. The inorganic oxide preferablycomprises a zeolite (for example, beta zeolite, ZSM-5) and/or alumina,and mixtures thereof. In some aspects, the support may comprise a betazeolite having a silicon to aluminum molar ratio between about 20 toabout 60.

There are a variety of ways for preparing the catalytic composite andincorporating the platinum metal, and optionally, the chloride therein.In one such method, the catalyst is prepared by impregnating the carriermaterial through contact with an aqueous solution of a water-solubledecomposable compound of the platinum group metal. In various aspects,the isomerization catalyst may comprise a Group X metal. In someaspects, the impregnation is carried out by contacting the carriermaterial in a solution of tetra amine platinum chloride, potassiumhexachloroplatinate, or any combination thereof. Other solutions maycomprise chloroplatinic acid, ammonium chloroplatinate, bromoplatinicacid, or platinum dichloride. Use of the platinum chloride compound mayincorporate the platinum component and at least a minor quantity of thechloride into the catalyst.

Other suitable isomerization catalyst compositions for use in thepresent systems and methods may comprise a Group VIII noble metal, ahydrogen form crystalline aluminosilicate, and a refractory inorganicoxide. The Group VIII noble metal may be incorporated into the catalyticcomposite as described above to supply the hydrogenation-dehydrogenationfunction. The Group VIII noble metal is present in an amount from about0.1 to about 5% by weight of the composite. The catalytic composite mayalso contain a catalytically effective amount of a promoter metal suchas tin, lead, germanium, cobalt, nickel, iron, tungsten, chromium,molybdenum, bismuth, indium, gallium, cadmium, zinc, uranium, copper,silver, gold, tantalum, or one or more of the rare earth metals andmixtures thereof. The hydrogen form silica-alumina has either athree-dimensional or channel-pore-structure crystal lattice framework.The three-dimensional aluminosilicates include both synthetic andnaturally occurring silica aluminas, such as, the faujasites whichinclude X-type, Y-type, ultrastable-Y and the like. L-type, omega-type,and mordenite are examples of the channel-pore-structure crystallinealuminosilicates. Mordenite in either naturally occurring or syntheticform is preferred, particularly with a silica to alumina molar ratio ofat least 16:1.

Operating conditions within the isomerization reactors of theisomerization reactor system 122 are selected to convert the highlybranched hydrocarbons to selectively convertible components. In someaspects, temperatures within the isomerization reactors of theisomerization reactor system 122 may range from about 200° C. to about350° C., or from about 275° C. to about 325° C. Higher reactiontemperatures may favor equilibrium mixtures of normal alkanes versusisoalkanes. The isomerization reactor system 122 may be maintained overa wide range of pressures. Pressure conditions in the isomerizationreactor system 122 may be between about 50 psig and about 300 psig, orabout 75 psig to about 125 psig. The rate of the feed stream (e.g., inthe highly branched hydrocarbons stream in line 118 and any optionalinlet streams in line 124) to the isomerization reactor or reactors mayvary over a wide range. In a number of aspects, the liquid hourly spacevelocity (LHSV) may range from about 0.5 hr⁻¹ to about 10 hr⁻¹, or fromabout 1 hr⁻¹ to about 4 hr⁻¹, or about 2 hr⁻¹.

When hydrogen is introduced as part of the isomerization reaction, thehydrogen may be combined with the inlet stream prior to entering theisomerization reactor system 122, and/or the hydrogen may be introducedprior to one or more isomerization reactors of the isomerization reactorsystem. The hydrogen may be introduced at a molar ratio of the hydrogento the highly branched hydrogen of between about 0.1 and about 10,between about 1 and about 5, or at about 2.

An isomerized stream may pass out of the isomerization reactor system122 through line 126. The conversion of the highly branched hydrocarbonsin the isomerization reactor system 122 may be capable of converting atleast about 70 wt. %, least about 75 wt. %, or at least about 80 wt. %,(the lowest is about the equilibrium value of 75 wt. % in total, butnormally about 80 wt. % with the highest of about 83 wt. %-84 wt. %,during the Time-on-stream test of as long as 100 h.) of the highlybranched hydrocarbons in the inlet streams to the isomerization reactorsystem 122 to selectively convertible components, based on the totalweight of the highly branched hydrocarbons in all of the feed streams tothe isomerization reactor system 122. In several aspects of thedisclosure, the isomerized stream may comprise between about 5 wt. % andabout 50 wt. %, or about 10 wt. % and about 40 wt. %, or about 15 wt. %and about 25 wt. % highly branched hydrocarbons

The isomerized stream in line 126 may pass to the inlet of thearomatization reactor system 106. The isomerized stream may be combinedwith the fresh hydrocarbon stream 102 prior to entering thearomatization reactor system 106 or directly enter one or more reactionsections within the aromatization reactor system 106. Within thearomatization reactor system 106, at least a portion of the selectivelyconvertible components produced in the isomerization reactor system 122may be converted to aromatic components.

The aromatization system 100 includes the separation of the aromaticproducts of the aromatization reaction prior to the separation of thehighly branched hydrocarbons from the selectively convertiblecomponents. In some aspects, the separation sequence may be reversed toseparate the highly branched hydrocarbons from the selectivelyconvertible components and the aromatic product prior to separating thearomatic components from the remaining selectively convertiblecomponents and aromatic products. Such an aromatization system 200 forconverting the selectively convertible components to aromatic productsis illustrated in FIG. 2. The system 200 of FIG. 2 is similar to thearomatization system 100 of FIG. 1, and similar streams and processes orzones will not be described in the interest of brevity. As shown in FIG.2, the fresh hydrocarbon stream 102 may enter the system 200 and pass tothe aromatization reactor system 106. The aromatization product streamin line 108 from the aromatization reactor system 106 may pass to a gasseparation zone 107 through line 105, where an optional hydrogen recyclestream can pass through line 130 and a hydrogen product stream can passthrough line 109. The remaining aromatic product can pass through line108 to a HBH separation zone 216 that is configured to process a rawaromatization product and separate the highly branched hydrocarbons fromthe unreacted selectively convertible components, and the aromaticproducts. The HBH separation zone 216 may be the same or similar to theHBH separation zone 116 described with respect to FIG. 1, and any of theseparation processes described with respect to the HBH separation zone116 of FIG. 1 may be used in the HBH separation zone 216. The streamrich in the highly branched hydrocarbons, the HBH rich stream, in line202 may pass to an isomerization reactor system 122, and the streamcomprising the unreacted selectively convertible components and aromaticproducts may pass to an aromatic separation zone 210.

The separation within the HBH separation zone 216 may separate at leastabout 60 wt. %, at least about 70 wt. %, at least about 80 wt. %, atleast about 90 wt. % or at least about 95 wt. % of the highly branchedhydrocarbons in the aromatization product stream in line 108 into thestream rich in the highly branched hydrocarbons passing out of the HBHseparation zone 216 in line 202. In other aspects of the disclosure, theseparation within the HBH separation zone 216 may separate at leastabout 60 wt. %, at least about 70 wt. %, at least about 80 wt. %, atleast about 90 wt. % or at least about 95 wt. % of the dimethylbutanesin the aromatization product stream in line 108. The concentration ofthe highly branched hydrocarbons in line 202 may be greater than about50 wt. %, greater than about 60 wt. %, greater than about 70 wt. %, orgreater than about 80 wt. %, based on the total weight of all of thecomponents of the stream in line 202.

The stream rich in the highly branched hydrocarbons may pass to anisomerization reactor system 122 that may be the same as or similar tothe isomerization reactor system 122 described with respect to FIG. 1.One or more additional streams comprising highly branched hydrocarbonsmay optionally be provided to the isomerization reactor system 122. Theresulting effluent from the isomerization reactor system 122 may pass tothe inlet of the aromatization reactor system 106 as described herein.

The stream comprising the unreacted selectively convertible componentsand aromatic products may pass to an aromatic separation zone 210. Thestream in line 204 may predominately comprise one or more selectivelyconvertible components (for example, unreacted selectively convertiblecomponents from the aromatization reactor system 106, by-products) andthe aromatic product from the aromatization reactor system 106. Thearomatic separation zone 210 may separate the stream into a raffinatestream in line 206 and an aromatic stream in line 208. The aromaticseparation zone may be the same as or similar to the aromatic separationzone 110 described with respect to FIG. 1, and any of the separationprocesses described with respect to the aromatic separation zone 110 inFIG. 1 may be used with the aromatic separation section 210.

The resulting raffinate stream in line 206 may be rich in selectivelyconvertible components that may optionally be recycled to the inlet ofthe aromatization reaction zone 106. The aromatic stream in line 208 maybe rich in the aromatic product from the aromatization reactor system106 and may pass out of the system 200 as a product stream. One or moreadditional treatment processes may be performed on the aromatic productstream prior to the aromatic product stream leaving the system.

Referring to FIG. 1 and FIG. 2, an aromatization process may be carriedout using the aromatization system 100 or 200. In various aspects of thedisclosure, a process for aromatizing hydrocarbons may includeconverting at least a portion of the highly branched hydrocarbons in afeed stream into selectively convertible components. For example, anisomerization reaction may be used to convert the highly branchedhydrocarbons into selectively convertible components. The isomerizationreaction may be carried out by contacting the feed stream comprising thehighly branched hydrocarbons with an isomerization catalyst contained inat least one isomerization reactor within an isomerization reactorsystem 122 under isomerization reaction conditions. The resultingreaction may isomerize a portion of the highly branched hydrocarbons inthe feed stream into the selectively convertible components.

The resulting effluent stream from isomerization reactor system may thenpass to an aromatization zone to undergo an aromatization reaction, asdescribed in more detail herein. In various aspects of the disclosure,the selectively convertible components in the isomerized stream in line126 may contact a dehydrocyclization catalyst in an aromatizationreactor system 106 under aromatization reaction conditions to convertthe selectively convertible components into one or more aromaticcomponents. The resulting effluent stream may comprise an aromaticproduct as a result of at least a portion of the selectively convertiblecomponents being converted into aromatic components along withunconverted selectively convertible components and some amount of highlybranched hydrocarbons.

In some aspects, the aromatization reactor effluent may pass to an HBHseparation zone 216 where at least a portion of highly branchedhydrocarbons may be separated to obtain a highly branched hydrocarbonstream passing through line 202 that has an increased highly branchedhydrocarbon concentration compared to the aromatization reactoreffluent. The highly branched hydrocarbon stream may be provided to theisomerization reactor system 122 as the feed stream. The remainingstream passing from the HBH separation zone 216 may pass to an aromaticseparation zone 210, where the aromatic product may be separated fromthe remaining stream. The aromatic product stream passing through line208 may have an increased aromatic concentration as compared to thestream passing to the aromatic separation section through line 204. Asecond stream comprising the selectively convertible components in line206 may also be recovered from the aromatic separation section. Thesecond stream may have an increased selectively convertible componentcontent as compared to the stream passing to the aromatic separationsection through line 204, and the second stream may be recycled to thearomatization reaction for further conversion.

In various aspects of the process for aromatizing hydrocarbons, thehighly branched hydrocarbons may be recovered from an aromatizationreactor effluent, and converting at least a portion of the highlybranched hydrocarbons into selectively convertible components. Thehighly branched hydrocarbons may be converted to selectively convertiblecomponents by contacting the highly branched hydrocarbons with anisomerization catalyst contained in at least one isomerization reactorwithin an isomerization reaction process, and isomerizing at least theportion of the highly branched hydrocarbons into the selectivelyconvertible components.

The resulting stream from the isomerization reactor system may be fed toan inlet of an aromatization reaction process to aromatize theselectively convertible components and produce an aromatic product. Theeffluent stream from the aromatization process may be separated toobtain an aromatic product stream and a stream enriched in the highlybranched hydrocarbons. The stream enriched in the highly branchedhydrocarbons may be recycled to the isomerization reactor system toproduce selectively convertible components that may be further reactedto form aromatic products.

In still other aspects of the disclosure, selectively convertiblecomponents may be converted to aromatic hydrocarbons by concentratinghighly branched hydrocarbons in a hydrocarbon stream to yield a highlybranched hydrocarbon stream that is enriched in highly branchedhydrocarbons. In various aspects, the highly branched hydrocarbons maybe concentrated by separating aromatics from the hydrocarbon stream toyield the highly branched hydrocarbon stream. In various aspects, thehighly branched hydrocarbons may be concentrated by separating one ormore highly branched hydrocarbons from the hydrocarbon stream to yieldthe highly branched hydrocarbons rich stream.

Once concentrated, at least a portion of the highly branchedhydrocarbons in the highly branched hydrocarbon stream may be convertedinto selectively convertible components. The highly branchedhydrocarbons may be converted by contacting the highly branchedhydrocarbons with an isomerization catalyst contained in at least oneisomerization reactor within an isomerization reactor system, which mayconvert at least the portion of the highly branched hydrocarbons intothe selectively convertible components. The resulting selectivelyconvertible components may then be passed to an aromatization reactionprocess wherein at least a portion of the selectively convertiblecomponents may be converted to aromatic products.

The system and methods described herein allow a dehydrocyclizationreaction to proceed using a variety of feed streams, including thosecomprising highly branched hydrocarbons. The process also reduces theneed for difficult separation processes to remove the highly branchedhydrocarbons within the system, which may be difficult to separate fromthe selectively convertible components due to close boiling points. As aresult of including the isomerization reactor system, feed streams maybe used from a broader range of sources. In some instances, feed streamshaving a high level of highly branched hydrocarbons may be fed to theisomerized reactor system prior to entering the aromatization reactorsystem. Thus, the system provided herein may provide an advantage overprior systems that may not process the highly branched hydrocarbonspresent in the feed stream.

EXAMPLES

The disclosure having been generally described, the following examplesare given as particular aspects of the disclosure and to demonstrate thepractice and advantages thereof. It is understood that the examples aregiven by way of illustration and are not intended to limit thespecification or the claims in any manner.

In the following examples, the β zeolite samples of the powder form(H-BEA 25, sample No. 11-00534/04, SiO₂/Al₂O₃=25) and extrudate form(T4546, 1/16″, sample No. 10740-S) were commercially available fromClariant.

Example 1

In a first example, an isomerization catalyst as described herein wasprepared and demonstrated, The catalyst was prepared by incipientwetness impregnation method, using 0.0857 g tetra ammine platinumchloride in 8.6 g distilled H₂O solution impregnated on 10 g β zeoliteof the powder form. The obtained sample was dried at room temperaturefor 16 hours, then dried at 120° C. for 2 hours (with a ramping rate of5° C./min) followed by a calcination at 500° C. for 4 hours (with aramping rate of 5° C. min).

The typical results showed about an average 91.1% 2,3-dimethylbutane(2,3-DMB) conversion and 81.4% total C₆ convertibles yield (including2-methylpentane, 3-methylpentane, n-hexane, methyl-cyclopentane andcyclohexane) at about 40 hours-on-stream at 100 psig, 300° C., 2 hr⁻¹LHSV and 2 H₂/HC. The results are shown in FIG. 3, which graphicallyillustrates the 2,3-DMB conversion and C₆ convertibles yield over the0.5% Pt/β-Zeolite catalyst.

Example 2

This example shows another isomerization catalyst. The catalyst wasprepared by incipient wetness impregnation method, using 0.1246 gpotassium hexachloroplatinate in distilled 8.6 g H₂O solutionimpregnated on 10 g β zeolite of the powder form. The obtained samplewas dried at room temperature for 16 hours, then dried at 120° C. for 2hours (with a ramping rate of 5° C./min) followed by a calcination at500° C. for 4 hours (with a ramping rate of 5° C./min).

The typical results showed about an average 90.9% 2,3-DMB conversion and77.0% total C₆ convertibles yield (including 2-methylpentane,3-methylpentane, n-hexane, methyl-cyclopentane and cyclohexane) at about40 hours-on-stream at 100 psig, 300° C., 2 hr⁻¹ LHSV and 2 H₂/HC. Theresults are shown in FIG. 4, which graphically illustrates the 2,3-DMBconversion and C₆ convertibles yield over the 0.5% Pt/β-Zeolitecatalyst.

Example 3

This example shows still another isomerization catalyst. The catalystwas prepared by incipient wetness impregnation method, using 0.1714 gtetra ammine platinum chloride in distilled 12.1 g H₂O solution (PHvalue modified by ammonia to 6.5-7) impregnated on 20 g β zeolite of theextrudate form. The obtained sample was dried at room temperature for 16hours, then dried at 120° C. for 2 hours (with a ramping rate of 5°C./min) followed by a calcination at 500° C. for 4 hours (with a rampingrate of 5° C./min).

The results are shown in FIG. 5, which graphically illustrates the2,3-DMB conversion and C₆ convertibles yield over 0.5% Pt/β-Zeolitecatalyst at 100 psig, 300° C., 2 hr⁻¹ LHSV and 2 H₂/HC.

Example 4

This example shows another isomerization catalyst. The catalyst wasprepared by incipient wetness impregnation method, using 0.2492 gpotassium hexachloroplatinate in distilled 12.1 g H₂O solutionimpregnated on 20 g β zeolite of the extrudate form. The obtained samplewas dried at room temperature for 16 hours, then dried at 120° C. for 2hours (with a ramping rate of 5° C./min) followed by calcination at 500°C. for 4 hours (with a ramping rate of 5° C./min).

The results are shown in FIG. 6, which graphically illustrates the2,3-DMB conversion and C₆ convertibles yield over 0.5% Pt/β-Zeolitecatalyst at 100 psig, 300° C., 2 hr⁻¹ LHSV and 2 H₂/HC.

Example 5

This example shows another isomerization catalyst. The catalyst wasprepared by incipient wetness impregnation method, using 0.1714 g tetraammine platinum chloride in 5.6 g distilled H₂O solution impregnated onZSM-5 zeolite (Si/Al=55) of the powder form. The obtained sample wasdried at room temperature for 16 hours, then dried at 120° C. for 2hours (with a ramping rate of 5° C./min) followed by a calcinations at500° C. for 4 hours (with a ramping rate of 5° C./min).

The results are shown in FIG. 7, which graphically illustrates the2,3-DMB conversion and C₆ convertibles yield over 0.5% Pt/ZSM-5(Si/AI=55) catalyst at 100 psig, 300° C., 2 LHSC and 2 H₂/HC.

Example 6

This example shows still another isomerization catalyst. The catalystwas prepared by incipient wetness impregnation method, using 0.0853 gtetra ammine platinum chloride in 5.5 g distilled H₂O solutionimpregnated on 10 g ZSM-5 zeolite (Si/AI=30) of the powder form. Theobtained sample was dried at room temperature for 16 hours, then driedat 120° C. for 2 hours (with a ramping rate of 5° C./min) followed by acalcinations at 500° C. for 4 hours (with a ramping rate of 5° C./min).

The results are shown in FIG. 8, which graphically illustrates the2,3-DMB conversion and C₆ convertibles yield over 0.5% Pt/ZSM-5(Si/AI=30) catalyst at 100 psig, 293° C., 2 LHSC and 2 H2/HC.

ADDITIONAL EMBODIMENTS

The following are non-limiting, specific aspects in accordance with thepresent disclosure:

In a first aspect, a process for aromatizing hydrocarbons comprises:converting at least a portion of highly branched hydrocarbons in a feedstream into convertible components; and aromatizing the selectivelyconvertible components to produce an aromatization reactor effluent,wherein the aromatization reactor effluent comprises an aromaticproduct.

A second aspect may include the process of the first aspect, whereinconverting at least the portion of the highly branched hydrocarbons intothe selectively convertible components comprises: contacting the feedstream with an isomerization catalyst in an isomerization reactor withinin an isomerization reactor system under isomerization reactionconditions; and isomerizing the portion of the highly branchedhydrocarbons in the feed stream into the selectively convertiblecomponents.

A third aspect may include the process of the second aspect, wherein theisomerization catalyst comprises a β zeolite.

A fourth aspect may include the process of the third aspect, wherein theisomerization catalyst comprises a Group 10 metal.

A fifth aspect may include the process of the third or fourth aspect,wherein the isomerization catalyst comprises between about 0.1 wt. % andabout 1 wt. % platinum on the β zeolite.

A sixth aspect may include the process of any of the third to fifthaspects, wherein a silicon to aluminum molar ratio of the β zeolite isbetween about 20 to about 60.

A seventh aspect may include the process of any of the first to sixthaspects, wherein the highly branched hydrocarbons comprise hydrocarbonshaving six or seven carbon atoms with an internal quaternary carbon, orhydrocarbons having six carbon atoms and two adjacent internal tertiarycarbons, or mixtures thereof.

An eighth aspect may include the process of the seventh aspect, whereinthe highly branched hydrocarbons comprise dimethylbutanes,trimethylbutanes, dimethylpentanes, or mixtures thereof.

A ninth aspect may include the process of the seventh aspect, whereinthe highly branched hydrocarbons comprise 2,2-dimethylbutane,2,3-dimethylbutane, 2,2,3-trimethylbutane 2,2-dimethylpentane,2,3-dimethylpentane. 2,2-dimethylhexane, 2,3-dimethylhexane, or mixturesthereof.

A tenth aspect may include the process of any of the first to ninthaspects, wherein the selectively convertible components may comprisehydrocarbons having six or seven carbon atoms without an internalquaternary carbon or hydrocarbons having six carbon atoms and withouttwo adjacent internal tertiary carbons, or mixtures thereof.

An eleventh aspect may include the process of any of the first to ninthaspects, wherein the selectively convertible components may comprisemethylpentanes, methylhexanes, or mixtures thereof.

A twelfth aspect may include the process of any of the first to ninthaspects, wherein the selectively convertible components may comprise atleast one of 2-methylpentane, 3-methylpentane, n-hexane, 2-methylhexane,3-methylhexane, n-heptane, or mixtures thereof.

A thirteenth aspect may include the process of any of the first totwelfth aspects, wherein the feed stream comprises between about 0.1 wt.% and about 100 wt. % highly branched hydrocarbons.

A fourteenth aspect may include the process of any of the first tothirteenth aspects, wherein aromatizing the selectively convertiblecomponents comprises: contacting the selectively convertible componentswith a dehydrocyclization catalyst in an aromatization reactor systemunder aromatization reaction conditions; and converting the selectivelyconvertible components into one or more aromatics in the aromaticproduct.

A fifteenth aspect may include the process of the fourteenth aspect,wherein the dehydrocyclization catalyst comprises at least one GroupVIII metal and zeolitic support.

A sixteenth aspect may include the process of the fifteenth aspect,wherein the least one Group VIII metal comprises platinum and thezeolitic support comprises silica bound L-zeolite.

A seventeenth aspect may include the process of the fifteenth orsixteenth aspect, wherein the dehydrocyclization catalyst comprises oneor more halogens.

An eighteenth aspect may include the process of any of the first toseventeenth aspects, wherein the aromatization reactor effluentcomprises the highly branched hydrocarbons, and wherein the processfurther comprises: separating at least a portion of the aromatic productfrom the aromatization reactor effluent to obtain a raffinate stream,wherein the raffinate stream has an increased highly branchedhydrocarbon concentration compared to the aromatization reactoreffluent; and providing the raffinate stream to the isomerizationreactor system as the feed stream.

A nineteenth aspect may include the process of any of the first toseventeenth aspects, wherein the aromatization reactor effluentcomprises the highly branched hydrocarbons, wherein the process furthercomprises: separating at least a portion of the aromatic product fromthe aromatization reactor effluent to obtain a raffinate stream, whereinthe raffinate stream has an increased highly branched hydrocarbonconcentration compared to the aromatization reactor effluent; andseparating the highly branched hydrocarbons from the raffinate stream toobtain the feed stream to the isomerization reactor system, wherein thefeed stream has an increased highly branched hydrocarbon concentrationcompared to the lean raffinate stream.

A twentieth aspect may include the process of any of the first toseventeenth aspects, wherein the aromatization reactor effluentcomprises the highly branched hydrocarbons, and wherein the processfurther comprises: separating at least a portion of the highly branchedhydrocarbons from the aromatization reactor effluent to obtain a highlybranched hydrocarbon stream, wherein the highly branched hydrocarbonstream has an increased highly branched hydrocarbon concentrationcompared to the aromatization reactor effluent; and providing the highlybranched hydrocarbon stream to the isomerization reactor system as thefeed stream.

In a twenty first aspect, a process for aromatizing hydrocarbonscomprises: recovering highly branched hydrocarbons from an aromatizationreactor effluent; converting at least a portion of the highly branchedhydrocarbons into selectively convertible components; and aromatizingthe selectively convertible components to produce an aromatic product.

A twenty second aspect may include the process of the twenty firstaspect, further comprising: feeding the selectively convertiblecomponents to an inlet of an aromatization reactor system, wherein thearomatization reactor system produces the aromatization reactoreffluent.

A twenty third aspect may include the process of the twenty secondaspect, wherein aromatizing the selectively convertible componentsoccurs within the aromatization reactor system.

A twenty fourth aspect may include the process of any of the twentyfirst to twenty third aspects, wherein converting at least the portionof the highly branched hydrocarbons comprises: contacting the highlybranched hydrocarbons with an isomerization catalyst; and isomerizing atleast the portion of the highly branched hydrocarbons into theselectively convertible components.

A twenty fifth aspect may include the process of the twenty fourthaspect, wherein the isomerization catalyst comprises a β zeolite and aGroup 10 metal.

A twenty sixth aspect may include the process of any of the twenty firstto twenty fifth aspects, wherein the selectively convertible componentsmay comprise at least one of 2-methylpentane, 3-methylpentane, orn-hexane.

In a twenty seventh aspect, a process for aromatizing hydrocarbonscomprises: concentrating highly branched hydrocarbons in a hydrocarbonstream to yield a highly branched hydrocarbon rich stream; converting atleast a portion of the highly branched hydrocarbons in the highlybranched hydrocarbon rich stream into selectively convertiblecomponents; and aromatizing the selectively convertible components toproduce an aromatization reactor effluent comprising an aromaticproduct.

A twenty eighth aspect may include the process of the twenty seventhaspect, wherein concentrating the highly branched hydrocarbons comprisesseparating aromatics from the hydrocarbon stream to yield the highlybranched hydrocarbons rich stream.

A twenty ninth aspect may include the process of the twenty seventh ortwenty eighth aspect, wherein concentrating the highly branchedhydrocarbons comprises separating at least a portion of the highlybranched hydrocarbons from the hydrocarbon stream to yield the highlybranched hydrocarbons rich stream.

A thirtieth aspect may include the process of any of the twenty seventhto twenty ninth aspects, wherein the hydrocarbon stream is thearomatization reactor effluent.

A thirty first aspect may include the process of any of the twentyseventh to thirtieth aspects, wherein converting at least the portion ofthe highly branched hydrocarbons into selectively convertible componentscomprises: contacting the highly branched hydrocarbons with anisomerization catalyst; and isomerizing at least the portion of thehighly branched hydrocarbons into the selectively convertiblecomponents.

A thirty second aspect may include the process of the thirty firstaspect, wherein the isomerization catalyst comprises a β zeolite andplatinum.

In a thirty third aspect, an aromatization reactor system comprises: atleast one aromatization reactor comprising a dehydrocyclizationcatalyst, a feed inlet, and an aromatization reactor effluent outlet; aseparator in fluid communication with the aromatization reactor effluentoutlet, wherein the separator is configured to separate at least aportion of an aromatization reactor effluent stream comprising anaromatic product and highly branched hydrocarbons into an aromaticproduct stream enriched in aromatics and a highly branched hydrocarbonstream enriched in the highly branched hydrocarbons, wherein theseparator is configured to pass the highly branched hydrocarbon streamout of a highly branched hydrocarbon stream outlet; and an isomerizationreactor system comprising at least one isomerization reactor furthercomprising an isomerization catalyst, wherein the isomerization reactorsystem is in fluid communication with the highly branched hydrocarbonstream outlet to receive the highly branched hydrocarbon stream; whereinthe isomerization reactor system is configured to isomerize at least aportion of the highly branched hydrocarbons in the highly branchedhydrocarbon stream into selectively convertible components, wherein anoutlet of the isomerization reactor system is in fluid communicationwith the feed inlet of the aromatization reactor system to pass at leasta portion of the selectively convertible components from theisomerization reactor system to the aromatization reactor system.

A thirty fourth aspect may include the system of the thirty thirdaspect, wherein the isomerization catalyst comprises a β zeolite.

A thirty fifth aspect may include the system of the thirty fourthaspect, wherein a silicon to aluminum molar ratio of the β zeolite isbetween about 20 to about 60.

A thirty sixth aspect may include the system of any of the thirty thirdto thirty fifth aspects, wherein the isomerization catalyst comprises aGroup 10 metal.

A thirty seventh aspect may include the system of any of the thirtythird to thirty sixth aspects, wherein the isomerization catalystcomprises between about 0.1 wt. % and about 1 wt. % platinum on the βzeolite.

A thirty eighth aspect may include the system of any of the thirty thirdto thirty seventh aspects, wherein the dehydrocyclization catalystcomprises at least one Group VIII metal and zeolitic support.

A thirty ninth aspect may include the system of the thirty eighthaspect, wherein the least one Group VIII metal comprises platinum andthe zeolitic support comprises silica bound L-zeolite.

A fortieth aspect may include the system of the thirty eighth or thirtyninth aspect, wherein the dehydrocyclization catalyst comprises one ormore halogens.

While the present disclosure has been illustrated and described in termsof particular apparatus and methods of use, it is apparent thatequivalent techniques, components and constituents may be substitutedfor those shown, and other changes may be made within the scope of thepresent disclosure as defined by the appended claims.

The particular aspects disclosed herein are illustrative only, as thedisclosure may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. Furthermore, no limitations are intended to thedetails of construction or design herein shown, other than as describedin the claims below. It is therefore evident that the particular aspectsdisclosed above may be altered or modified and all such variations areconsidered within the scope and spirit of the disclosure. Accordingly,the protection sought herein is as set forth in the claims below.

We claim:
 1. A process for aromatizing hydrocarbons comprising: concentrating highly branched hydrocarbons in a hydrocarbon stream to yield a highly branched hydrocarbon rich stream, wherein the highly branched hydrocarbons comprise hydrocarbons having six or seven carbon atoms with an internal quaternary carbon or hydrocarbons having six carbon atoms and two adjacent internal tertiary carbons, or mixtures thereof; converting at least a portion of the highly branched hydrocarbons in the highly branched hydrocarbon rich stream into selectively convertible components by contacting the highly branched hydrocarbons with an isomerization catalyst and isomerizing at least the portion of the highly branched hydrocarbons into the selectively convertible components; and aromatizing the selectively convertible components to produce an aromatization reactor effluent comprising an aromatic product.
 2. The process of claim 1, wherein the isomerization catalyst comprises platinum.
 3. The process of claim 1, wherein the isomerization catalyst comprises a platinum alumina catalyst with or without a Friedel-Crafts halide, platinum molecular sieve catalyst, or platinum sulfate metal oxide catalyst.
 4. The process of claim 1, wherein the isomerization catalyst comprises a chlorided platinum alumina catalyst.
 5. The process of claim 4, wherein alumina comprises an anhydrous gamma-alumina.
 6. The process of claim 4, wherein the chloride component is present in an amount from about 2 wt. % to about 10 wt. % based upon weight of dry support material.
 7. The process of 2, wherein isomerization catalyst comprises from about 0.01 wt. % to about 5 wt. % of the platinum.
 8. The process of claim 7, wherein the isomerization catalyst further comprises at least one noble metal selected from the group consisting of palladium, ruthenium, rhodium, osmium, and iridium.
 9. The process of claim 8, wherein the isomerization catalyst comprises the at least one noble metal in a concentration of from 0.01 wt. % to about 5 wt. %.
 10. The process of claim 1, wherein concentrating the highly branched hydrocarbons comprises separating aromatics from the hydrocarbon stream to yield the highly branched hydrocarbons rich stream.
 11. The process of claim 1, wherein concentrating the highly branched hydrocarbons comprises separating at least a portion of the highly branched hydrocarbons from the hydrocarbon stream to yield the highly branched hydrocarbons rich stream.
 12. The process of claim 1, wherein the hydrocarbon stream is the aromatization reactor effluent and the process comprises separating at least a portion of the aromatic product from the aromatization reactor effluent to obtain a raffinate stream; separating at least a portion of the highly branched hydrocarbons from the raffinate stream to to yield the highly branched hydrocarbons rich stream.
 13. An aromatization reactor system comprises: at least one aromatization reactor comprising a dehydrocyclization catalyst, a feed inlet, and an aromatization reactor effluent outlet; a separator in fluid communication with the aromatization reactor effluent outlet, wherein the separator is configured to separate at least a portion of an aromatization reactor effluent stream comprising an aromatic product and highly branched hydrocarbons into an aromatic product stream enriched in aromatics and a highly branched hydrocarbon stream enriched in the highly branched hydrocarbons, wherein the separator is configured to pass the highly branched hydrocarbon stream out of a highly branched hydrocarbon stream outlet; and an isomerization reactor system comprising at least one isomerization reactor further comprising an isomerization catalyst, wherein the isomerization reactor system is in fluid communication with the highly branched hydrocarbon stream outlet to receive the highly branched hydrocarbon stream; wherein the isomerization reactor system is configured to isomerize at least a portion of the highly branched hydrocarbons in the highly branched hydrocarbon stream into selectively convertible components, wherein an outlet of the isomerization reactor system is in fluid communication with the feed inlet of the aromatization reactor system to pass at least a portion of the selectively convertible components from the isomerization reactor system to the aromatization reactor system.
 14. The system of claim 13, wherein the isomerization catalyst comprises a β zeolite.
 15. The system of claim 13, wherein the isomerization catalyst comprises a Group 10 metal.
 16. The system of claim 13, wherein the isomerization catalyst comprises between about 0.1 wt. % and about 1 wt. % platinum on the β zeolite.
 17. The system of claim 13, wherein the isomerization catalyst comprises a platinum alumina catalyst with or without a Friedel-Crafts halide, platinum molecular sieve catalyst, or a platinum sulfate metal oxide catalyst.
 18. The system of claim 13, wherein the dehydrocyclization catalyst comprises at least one Group VIII metal and zeolitic support.
 19. The system of claim 18, wherein the least one Group VIII metal comprises platinum; the zeolitic support comprises silica bound L-zeolite; and the dehydrocyclization catalyst further comprises one or more halogens.
 20. The system of claim 13, wherein the separator is further configured to concentrate the highly branched hydrocarbon stream to yield a highly branched hydrocarbon rich stream then passing the highly branched hydrocarbon rich stream out of the highly branched hydrocarbon stream outlet. 